Cardiovascular and sympathoadrenal responses to heat stress following water deprivation in rats

Michael P. Massett, David G. Johnson, Kevin C. Kregel

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

This study was designed to characterize the regional and systemic hemodynamic and sympathoadrehal responses to heating after 24 and 48 h of water deprivation in chloralose-anesthetized, male Sprague-Dawley rats (n = 7 per group). Water deprivation produced significant decreases in body weight of 8.1 and 13.7% in the 24- and 48-h groups (P < 0.05), respectively. After water deprivation, rats were exposed to an ambient temperature of 43°C. After correction for body weight differences, heating rates were faster in the 48-h group compared with both euhydrated and 24-h groups. Mean arterial blood pressure (MAP), heart rate, and colonic (T(co)) and tail (T(tail)) temperatures increased above baseline in all groups during heating. Renal and mesenteric artery blood flow velocities decreased, and vascular resistances increased in response to heating. Compared with euhydrated controls, 48-h water-deprived rats exhibited attenuated pressor (ΔMAP = 36 ± 3 vs. 18 ± 3 mmHg) and visceral vasoconstrictor (%Δ in mesenteric resistance = 122.6 ± 27.3 vs. 54.9 ± 6.9%) responses during heating. Tail-skin blood flow estimated from T(tail) was also lower at baseline and the onset of heating in water-deprived rats. However, peak T(tail) and T(co) values were similar across groups. Plasma catecholamines measured in separate groups of rats (n = 6 per group) were significantly higher at baseline and the end of heating in the 48-h group compared with euhydrated and 24-h groups. Despite this exaggerated sympathoadrenal response, the 48-h group exhibited attenuated hemodynamic responses to nonexertional heating compared with euhydrated and 24-h water-deprived rats. These data suggest that cardiovascular and thermoregulatory adjustments can compensate for small changes in hydration state (i.e., 24 h), but more severe levels of hypohydration significantly alter blood pressure and body temperature regulation during heat stress.

Original languageEnglish (US)
Pages (from-to)R652-R659
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume270
Issue number3 39-3
DOIs
StatePublished - 1996
Externally publishedYes

Keywords

  • blood pressure
  • catecholamines
  • hyperthermia
  • hypohydration
  • regional blood flows
  • temperature regulation

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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